An example of a conventional battery cartridge (hereinafter referred to as a battery pack) that has previously been disclosed in Japanese patent application No. 3-52555 to the same assignee of the present application will be described below.
FIG. 1 of the accompanying drawings shows battery charger 12 with a battery pack 10 attached and FIG. 2 shows an example of such battery charger 12 without a battery pack attached.
As illustrated, the battery charger 12 is a molded product of a plastic material and has a recessed portion 51 onto which the battery pack 10 is attached. The battery charger 12 comprises a primary circuit portion 52 having a power supply transformer or the like and a secondary circuit portion 53 having a rectifying circuit or the like. The battery charger 12 further includes an AC (alternating current) cord 54 having a plug connected to the primary circuit portion 52.
As shown in FIG. 2, the secondary circuit portion 53 includes an adaptor plug 55 from which a DC power is supplied, first and second terminals 56, 57 from which a charging power is supplied and a third terminal 58 from which a temperature detecting signal is input to the battery charger 12. The adaptor plug 55 is provided so that the electrical machinery and apparatus can be operated by directly utilizing a DC power supplied from the AC power supply instead of the battery pack 10.
The three terminals 56, 57 and 58 are formed as leaf springs so that they can be deformed flexibly. A spring constant of the third terminal 58 is selected to be substantially 2/3 of those of the first and second terminals 56, 57. The first, second and third terminals 56, 57, 58 are assembled into a molded plate 60 and the molded plate 60 is disposed on the bottom surface of the recessed portion 51. The molded plate 60 is colored a in proper color such as blue or the like, which is different from the color (black) of the case 59 of the battery pack 10.
The secondary circuit portion 53 includes a control circuit (not shown). The control circuit is operated to control the charging of the battery within the battery pack 10 and controls the charging state of the battery on the basis of a so-called- V charging completion method in which a voltage between the first and second terminals 56, 57 is progressively increased by the start of the charging and the charging is ended when the voltage is lowered a little after the voltage had reached the peak value.
The aforesaid control circuit detects the temperature of a battery that is being charged on the basis of a temperature detecting signal from a temperature detecting element provided on the bottom surface of the battery pack 10. When such detected temperature of the battery exceeds a predetermined value, the control circuit interrupts a charging current supplied from the first and second terminals 56, 57 to the battery thereby to disable the battery charger 12 from charging the battery.
As shown in FIG. 1, the battery pack 10 includes a casing 18 that comprises an upper casing 14 and a bottom casing 16. The casing 18 is so arranged as to accommodate therein a plurality of batteries.
FIGS. 3A and 3B show the battery pack 10 with cylindrical batteries 21 through 25 accommodated within the battery pack 10. More specifically, FIG. 3A is a diagram showing the inside of the battery pack 10 with the bottom casing 16 removed. FIG. 3B is a cross-sectional view taken along the line III--III in FIG. 3A.
The batteries 21 through 25 may be nickel-hydrogen secondary batteries and are arranged in parallel to one another as shown in FIGS. 3A and 3B. The electrodes of the batteries 21 to 25 are connected by means of conductive plates 32. Hence, the five batteries 21 to 25 are constructed as a combination battery 27 in which the batteries 21 to 25 are electrically connected in series. An insulating sheet 34 is disposed between the electrodes of the batteries 21 to 25 and the conductive plates 32.
The combination battery 27 includes first and second electrodes 36 and 38 of positive and negative polarities for effecting the charging and discharging. A temperature detecting element 42 such as a thermistor or the like and a breaker (not shown) are disposed under the two electrodes 36, 38. The first and second electrodes 36, 38, the temperature detecting element 42 and the breaker (not shown), etc., are supported by a molded member 44 disposed between the two batteries 21 and 22.
The electrodes 36, 38 of the combination battery 27 constitute output terminals of the battery pack 10. Hence, the electrodes 36, 38 will be referred to as output terminals 36, 38, if necessary.
A third electrode 40 that outputs a temperature detecting signal is further disposed under the battery 21. The third electrode 40 is formed as a thin plate that constitutes a leaf spring. The third electrode 40 may be directly bonded to the battery 21 by an adhesive or attached to the molded member 44.
Two lead wires 42A and 42B are connected to the temperature detecting element 42. The temperature detecting element 42 is connected to the first electrode 36 by means of the first lead wire 42A, and the temperature detecting element 42 is connected to the third electrode 40 by means of the second lead wire 42B.
The combination battery 27 and the three electrodes 36, 38 and 40 are disposed so as to contact with the inner surface of the upper casing 14.
FIG. 4 shows a configuration of the bottom surface of the casing 18, i.e., the outer surface of the bottom casing 16. The bottom casing 16 has on its outer surface eleven recessed portions 16A through 16K formed and three through-holes 16a, 16b and 16c bored therethrough. Of the three through-holes 16a, 16b and 16c, the two through-holes 16a, 16b are bored through the recessed portions 16D and 16E, respectively.
The three through-holes 16a, 16b, 16c are bored through the outer surface of the bottom casing 16 at their positions corresponding to the three electrodes 36, 38 and 40 of the battery pack 10. Therefore, when the upper casing 14 is covered with the bottom casing 16 to form the casing 18 and the batteries 21 to 25 are accommodated within the casing 18, the three electrodes 36, 38, 40 are exposed from the corresponding three throughholes 16a, 16b, 16c, respectively.
The eight recessed portions 16C through 16J and the two through-holes 16a, 16b are disposed in association with spacings 28A through 28D of the batteries 21 to 25.
As shown in FIG. 4, on the outer surface of the bottom casing 16, symbols +, - and .perp. encircled by the symbol .smallcircle., which are adjacent to the three electrodes 36, 38, 40, are formed. These symbols are formed by forming concavities and convexities on the form of the bottom casing 16 when the plastic material is molded.
The bottom casing 16 is colored in black and the portion within a dashed line 20 encircling the three through-holes 16a, 16b, 16c is colored in another color such as blue.
On the bottom surface of the recessed portion 51 of the battery charger 12, convexes portions 61A, 61B, 61C are formed. The convex portions 61A, 61B, 61C are disposed so as to be engaged with the corresponding recessed portions 16I, 16G, 16H of the battery pack 10.
Of such recessed portions 16I, 16G and 16H, the outside recessed portions 16I, 16G are referred to as detection apertures and the inside larger recessed portion 16H is referred to as a locking aperture. The detection apertures 16I, 16G function to detect whether or not the battery pack 10 is properly attached to the battery charger 12 or the like.
When the battery pack 10 is properly attached to the battery charger 12, the two convexed portions 61A, 61B are properly inserted into the detection apertures 16I, 16G, respectively. Whereas, when the battery pack 10 is not properly attached to the battery charger 12, the two convexed portions 61A, 61B are not inserted into the corresponding recessed portions 16I, 16G and the bottom surface of the battery pack 10 is caused to rise from the bottom surface of the recessed portion 51 of the battery charger 12.
The locking aperture 16H functions to support the battery pack 10 so that the battery pack 10 attached to the battery charger 12 is prevented from being moved uselessly during charging.
When the proper battery pack 10 is attached to the battery charger 12, the three electrodes 36, 38, 40 of the combination battery 27 exposed from the through-holes 16a, 16b, 16c of the bottom casing 16 are respectively brought in contact with the three terminals 56, 57, 58 of the battery charger 12.
Since either of the three electrodes 36, 38, 40 and the three terminals 56, 57, 58 are formed of the members that can be deformed with flexibility, e.g., leaf springs are described above, both of the three electrodes 36, 38, 40 and the three terminals 56, 57, 58 can be reliably brought in contact with one another by spring force of such resilient members. As described above, the spring constant of the third terminal 58 is selected to be small as compared with those of other remaining terminals 56 and 57 so that, even when the battery pack 10 without the third electrode 58 is attached to the battery charger 12, the bottom surface of the battery pack 10 can be protected from being damaged.
In the aforesaid example of the prior art, the bottom casing 16 of the battery pack 10 includes the detection apertures 16I, 16G and whether the battery pack 10 can be properly attached to the battery charger 12 is determined by detecting whether or not the convexed portions 61A, 61B on the bottom surface of the recessed portion 51 of the battery charger 12 are properly engaged with the detection apertures 16I, 16G. This arrangement can be can be utilized not only between the battery pack 10 and the battery charger 12 but also between the battery pack 10 and electrical machinery and apparatus that utilizes the battery pack 10 as a power source.
In the aforesaid battery pack 10, i.e., the output terminals 36, 38 are exposed from the apertures 16a, 16b.
When the battery pack 10 is not properly attached to the battery charger 12, the battery pack 10 is caused to rise from the battery charger 12 by an amount corresponding to the height of the convexed portions 61A, 61B and then inclined. If an inclination angle of the battery pack 10 is large, whether or not the battery pack 10 is properly attached to the battery charger 12 can easily be detected. If on the other hand, the inclination angle is small, then it becomes more difficult to detect whether or not the battery pack 10 is properly attached to the battery charger 12.
In order to increase the inclination angle, the heights of the convexed portions 61A, 61B of the battery charger 12 must be increased and the depths of the detection apertures 16I, 16G of the battery pack 10 must be increased, which, however, makes the molding treatment of the battery charger 12 and the bottom casing 16 impossible.
To increase the inclination angle of the battery pack 10 without changing the heights of the convexed portions 61A, 61B of the battery charger 12, the convexed portions 61A, 61B of the battery charger 12 and the detection apertures 16I, 16G of the battery pack 10 must be formed at the positions nearer to the center position.
In the aforesaid example of the prior art, as shown in FIG. 4, the detection apertures 16I, 16G are bored through the bottom casing 16 of the battery pack 10 side by side at one of its side portion and are not formed at the center thereof.
Further, the battery pack 10 has mounted thereon an identification marker (not shown) that indicates the condition that the battery was already utilized and charged. Such identification marker is disposed at a front end portion 16-1 (see FIG. 3B) of the bottom casing 16 of the battery pack 10 so that the dimension of the battery pack 10 is increased in its longitudinal direction by an amount corresponding to the protruded portion of the identification marker.
FIGS. 5A, 5B and FIGS. 6A, 6B show other examples of the conventional battery pack 10. In these examples of the conventional battery pack 10, the electrodes 36, 38, i.e., output terminals 36, 38, are disposed at positions different from those of the example shown in FIG. 4. However, the electrodes 36, 38, i.e., output terminals 36, 38, are both exposed on the outer surface of the casing 18. Thus, there is the risk that the batteries within the battery pack 10 will be damaged when the electrodes 36, 38, i.e., output terminals 36, 38, are short-circuited by conductive metal products such as a key ring, a necklace, a chain or the like.
It is another problem that dust or the like may collect on the electrodes which could result in the electrical connection between the electrodes and the connection terminals of the battery charger or electrical machinery and apparatus to fail.